1. Field of the Invention
The present invention relates to a camera into which a cartridge capable of distinguishing and indicating the usage state of the film may be loaded, and, in particular, to a camera that prevents the loading of a film cartridge that distinguishes and indicates that the film is used.
2. Description of Related Art
Japanese Laid-Open Patent Application No. 5-107633 discloses a film cartridge (referred to hereafter simply as "cartridge") capable of distinguishing and indicating the film usage state and a camera into which this cartridge can be loaded. The film usage state indicates whether there are no frames that have been photographed yet (unused film), whether the film has been taken out with only some of the frames photographed (partially used film), or whether all frames of the film have been photographed (completely used film).
In addition, the camera shown in the Japanese publication is equipped with a mechanism that prevents the loading of a cartridge that contains completely used film. This camera has a cartridge chamber into which a cartridge may be loaded by insertion in the axial direction. A loading prevention pin can project into the cartridge chamber or be withdrawn from the projected position. When a cartridge that indicates that the film is completely used is inserted into the cartridge chamber, the loading prevention pin stays in the projected position and prevents the loading of the cartridge. When cartridges that indicate film other than completely used film are being inserted into the cartridge chamber, the pin is withdrawn from the cartridge chamber and loading of the cartridge is allowed. The loading prevention pin is arranged so as to return to the projected position when the loaded cartridge is at least partially ejected (i.e.,
A mechanism may be provided that partially ejects the cartridge in the axial direction by hand operation to facilitate the removal of the cartridge from the cartridge chamber. However, if the cartridge is not ejected by a sufficient amount by this type of ejection mechanism, the loading prevention pin will not move to the projected position, and the film cartridge containing completely used film may be accidentally reloaded into the cartridge chamber. With an initial feed-type camera that automatically feeds the film upon occurrence of the film cartridge lid-closing action after the film has been loaded, the film of such a film cartridge that has been only partially ejected by the ejection mechanism and accidentally reloaded, will be initially advanced even if it contains completely used film, thereby resulting in the possibility of a double exposure.
With such a camera, even if the photographer notices the mistake of accidentally reloading the used film, the automatic feeding operation will occur, and the photographer will have to wait until a rewinding operation is performed before removing the film cartridge.